A wireless local area network (WLAN) is a data transmission system, and replaces, by using a radio frequency (RF) technology, a legacy local area network comprising a twisted-pair copper wire, so that a user can transmit information via the wireless local area network by using a simple access architecture. Development and application of a WLAN technology have greatly changed people's communication manner and working manner, and bring unprecedented convenience to people. Wide application of intelligent terminals is accompanied by people's growing requirements for data network traffic. Development of the WLAN depends on standard formulation, popularization, and application. The IEEE 802.11 family is primary standards, and mainly includes 802.11, 802.11b/g/a, 802.11n, and 802.11ac. In all standards except the 802.11 and the 802.11b, an orthogonal frequency division multiplexing (OFDM) technology is used as a core technology at a physical layer.
Channel estimation is a process of estimating, according to a receive signal and by a specific criterion, a parameter of a channel through which a transmit signal passes. Performance of a wireless communications system is affected by a wireless channel to a great extent, such as shadow fading and frequency selective fading. Consequently, a transmission path between a transmitter and a receiver is extremely complex. Unlike a wired channel that is fixed and predictable, the wireless channel is characterized by high randomness. A channel needs to be estimated in coherent detection of an OFDM system, and channel estimation precision directly affects performance of the entire system.
The WLAN technology has been rapidly developed over the past dozen of years, and a core transmission standard is the IEEE 802.11 family of standards that includes the 802.11a, the 802.11n, the 802.11ac, and the like. In addition, the 802.11 family of standards is backward-compatible, that is, a subsequently developed standard is compatible with an existing standard. Currently, 802.11ax in a standardization process also needs to have a backward compatibility feature. A peak-to-average ratio (PAPR) of the wireless local area network needs to be reduced as much as possible in a corresponding standard.